1. Field of the Invention
The present invention relates to a packet data transmission method in a CDMA mobile communication network and, more particularly, to a multicast and broadcast transmission method.
2. Background of the Related Art
Recently, with the remarkable development in mobile communication technology, mobile communication service providers have begun providing subscribers with improved functions and various kinds of services. The mobile communication service is expanding its service into the service area previously provided only by wired communication. In addition, research on faster and more effective methods and techniques is being conducted with respect to the transmission of service.
A multicast, one of multi-address calling, denominates a communication form made between one transmission side and a plurality of receiving sides in a network. For example, a multicast communication is like transmitting an e-mail message to all of the addresses stored in an address book. Multicasting is mostly used for teleconferencing, such as video-conferencing or audio-conferencing, in which one transmission party transmits an image or voice to a plurality of selected receiving-party sites. In the case of video-on-demand (VOD), a server transmits an image to a plurality of subscribers' set-top boxes. The multicast transmission method is currently used for mobile communication as a method for providing an e-mail receiving service to a subscriber or transmitting specific contents to a subscriber group. A broadcast is a method for transmitting the same data to a plurality of unspecified terminals. Contrasted with the multicast, a unicast is a communication form made between one transmitting party and one receiving party.
FIG. 1 is a drawing conceptually illustrating a multicast or a broadcast transmission in a CDMA mobile communication network, in accordance with the related art. In the case that an Internet server intends to transmit packet data to every terminal (or mobile station) of a mobile communication system network or to a plurality of mobile stations (MSs) of a particular multicast group, an IP datagram is transmitted to an MS by a multicast (or broadcast) method using a common signal channel or by a multicast (or broadcast) method through a PPP link. The base station controller (BSC) and the packet control function (PCF) are independent equipment, but for the sake of explanation, they are shown as one equipment block in the drawing.
The multicast (or broadcast) method using a common signal channel is not suitable for transmitting high speed multimedia, due to the channel's low speed and because the signal channel may be overloaded.
As for the multicast (or broadcast) method through the PPP link, which uses a similar transmission method and path to the unicast transmission, a packet data serving node (PDSN) sets an individual link to every target MS and transmits the multicast data.
Accordingly, when an arbitrary server multicasts or broadcasts data to a plurality of MSs on the Internet, since target MSs of the mobile communication network individually occupy a radio traffic channel, the multicasting method differs little from an individual line connection at the side of the mobile communication network.
FIG. 2 is a drawing illustrating a service connection (from an MS view) between radio protocol objects of a CDMA mobile communication system. The functional object of a radio protocol and a service interface includes a physical channel object 10, such as a common assignment channel (CACH), a common power control channel (CPCCH), a pilot channel (PCH), a common control channel (CCCH), a sync channel (SYNC), a fundamental traffic channel (FCH), a supplemental channel (SCH), a dedicated control channel (DCCH), a reverse access channel (R-ACH), a reverse enhanced access channel (R-EACCH), a broadcast control channel (BCCH), and a paging channel (PCH). The functional object of the radio protocol and the service interface also includes a logical channel object 20, such as a common signaling channel (csch) for transmitting a common signal, a dedicated signaling channel (dsch) for transmitting a control signal with an assigned MS, and a dedicated traffic channel (dtch) allocated to an assigned MS, for transmitting user data.
The multiplex and QoS sub-layer is positioned between the physical channel and the logical channel. This sub-layer includes a common channel multiplex sub-layer 30, which handles the common channel, and a multiplex sub-layer 40, which handles an individual channel assigned to the MS and controls the data multiplexing/demultiplexing of the logical channel and the physical channel. The multiplex and QoS sub-layer further controls a transmission quality.
A signaling radio burst protocol (SRBP) 50 is positioned between a signaling link access controller (LAC) 60 and the common channel multiplex sub-layer 30 and controls the processing of the radio frame data of a signaling message.
A radio link protocol (RLP) 70 controls an individual channel transmission so that the individual channel transmission of the packet data is reliable. The signaling LAC 60 controls the transmission process, so that a message of an upper signaling layer can be reliably transmitted to the other party, and also controls the authentication of a message.
The MS and the Base Station Transceiver Subsystem (BTS) transmit to and receive from each other a signal layer message of an upper layer and individual transmission data through a LAC sub-layer, a media access controller (MAC) sub-layer, and the physical layer. That is, the function object and the service interface of the radio protocol only include a forward/backward individual signal channel (f/r-dsch) and a forward/backward common signal channel (f/r-csch) for transmitting an MS control signal and a BTS information signal. Additionally, the function object and service interface only have a forward/backward individual channel (f/r-dtch) for individually transmitting data to a particular MS. The BTS necessarily has the physical channel, but the other channels in the middle process may exist in the BTS or the BSC according to a particular implementation.
The related art multicast service has many problems. For example, in the case that the Internet server multicasts (or broadcasts) to the MS of the mobile communication network, since every MS individually occupies the radio traffic channel, radio resources are substantially wasted. In addition, since a wired resource of a wired BTS-BSC/PCF-PDSN is occupied for every MS receiving the multicast (or broadcast), the occupancy of a separate radio traffic channel by every MS is very inefficient for the multicasting/broadcasting transmission, when transmitting the same message to a plurality of target MSs.